The objective of this training grant is to train biostatisticians to work in inter-disciplinary collaborative teams addressing the problems associated with explaining the effects of chemical mixtures. A key to the success of this venture is the joining of the efforts of key scientists (mixtures toxicologists and biostatisticians) in the field of chemical mixtures with trainees from a department of biostatistics. The goal is for trainees to gain an understanding of and experience working on statistical issues of mixtures of chemicals. These trainees will be qualified to hold unique positions in governmental agencies, academia, and industry where properly evaluating drug/chemical interactions is becoming increasingly important. The trainees will be Ph.D. students in the Department of Biostatistics at the Medical College of Virginia campus of Virginia Commonwealth University (VCU), where they will pursue doctoral training in the discipline of biostatistics. Additional expertise will be achieved through work on dissertation topics that are pertinent to the field of mixtures and through externships with toxicologists and/or risk assessors actively working in the area of chemical mixtures. Through these externship programs, students will gain experience collaborating with a team of experts working on studies involving chemical mixtures. The trainees will assist in the design of mixture studies, conduct appropriate power analyses, analyze resulting data and write reports for the preceptor with proper interpretation of the results. In addition, the trainees will collaborate with biostatisticians who are developing statistical methodology for issues involved in the design and analysis of data resulting from studies of mixtures of chemicals and who are conducting analyses of data from mixture studies.